Restoring Balance – Biological Control of Opuntia stricta at Ol Jogi

Across the semi-arid landscapes of Laikipia, the interplay between wildlife, vegetation, and soil is complex. When invasive plant species take hold, many important ecosystem processes are disrupted. At Ol Jogi Wildlife Conservancy, one such challenge emerged in the early 2010s with the rapid spread of Opuntia stricta, commonly known as prickly pear cactus.

Originally introduced as an ornamental plant, Opuntia stricta has become one of the most damaging invasive species in East African rangelands. At Ol Jogi, dense thickets began to spread across sections of the conservancy, suppressing native vegetation, altering grazing patterns, and degrading habitat for both wildlife and livestock. Left unchecked, the cactus had the potential to transform large areas of the landscape.

Traditional control methods, such as manual removal and chemical treatment, proved inefficient, costly, and potentially harmful to surrounding ecosystems. Recognising the need for a sustainable and ecologically sound solution, Ol Jogi turned to biological control.

In 2014, in partnership with the International Centre for Agriculture and Bioscience (CABI), Ol Jogi undertook a comprehensive environmental impact assessment and secured approval from Kenya’s National Environment Management Authority (NEMA). After strict quarantine protocols were followed, Ol Jogi became the first trial release site in Kenya for the biological control agent Dactylopius opuntiae, commonly known as cochineal.

Cochineal is a host-specific scale insect that feeds exclusively on cactus species within the Opuntia genus. The insects attach to cactus pads and feed on plant sap, gradually weakening the plant and reducing its ability to grow and reproduce. Because the insect targets only cactus species, the approach allows invasive populations to be reduced without harming surrounding vegetation.

To support the program, Ol Jogi established a greenhouse facility dedicated to cultivating cochineal colonies. While insects can disperse naturally through wind and wildlife movement, the conservancy also conducts targeted releases to accelerate control in heavily infested areas. Today, a team of six casual staff works on the project, assisting with cochineal propagation, field releases, and the monitoring and management of invasive plant species across the conservancy. We release more cochineal nearly every six weeks and can positively target about 34 hectares (84 acres) per year.

More than a decade after the initial introduction, the results have been remarkable. Areas once dominated by dense prickly pear thickets are beginning to recover as native grasses and shrubs return. This regeneration restores grazing for wildlife, improves habitat structure, and strengthens the ecological resilience of the land.

The program’s impact has extended beyond the boundaries of Ol Jogi itself. Cochineal from the conservancy has been shared with authorised recipients, including neighbouring conservancies, community lands, and the Kenya Wildlife Service, contributing to wider landscape-scale efforts to control Opuntia stricta across northern Kenya.

Today, the project forms part of Ol Jogi’s broader Invasive Alien Plant Species Management Plan, demonstrating how science-based conservation and long-term commitment can restore balance to fragile ecosystems.

Through careful ecological management, collaboration with scientific partners, and consistent field work, Ol Jogi continues to turn an invasive challenge into a story of restoration, strengthening the health of the land for wildlife, people, and future generations.